Embodiments of the present invention are generally related to RF matrix switching systems, and more particularly to provide a return path in a forward path RF matrix switching system for use in a cable television system.
The primary function of a switch fabric is to pass traffic between input and output interface cards (referred to as the “forward” direction). RF matrix switches are designed to connect input signals from multiple sources to any one of a set of output devices. Typically, an output may have only one input. The forward path input-to-output switching is managed via a controller that maps the inputs and outputs and allows for reconfiguration on the fly.
In a cable environment, RF matrix switches are used to switch signals from multiple head-ends to set top boxes (STBs) for testing and evaluation. Manufacturers of STBs are constantly revising and upgrading STBs to add functionality, improve performance, and to reduce manufacturing costs. It is important for cable providers to test STBs under “real-world” conditions using live signals from operating head-ends before placing such devices in service. However, changes in the real-world requirements for STBs have not been met with concomitant changes in RF matrix switch technology.
The earliest cable television (CATV) systems were, in effect, strategically placed antennas with very long coax cables connecting them to subscribers' television sets. Content was transmitted as an analog signal and the signal path was one-way from the cable head-end to the subscriber's terminal (that is, the “forward” direction). As the number of program options grew, the bandwidth of cable systems also increased. Early systems operated at 200 MHz, allowing 33 channels. As technology progressed, the bandwidth increased to 550 MHz, with the number of channels increasing to 91.
In 1976, the coax trunk cables that carry signals from the CATV head-end to distribution nodes were replaced with fiber-optic cables, leaving only the drop to the subscriber as copper-based. The hybrid fiber network (HFN) offered many advantages over the pure copper-coax cable networks. From a technical perspective, fiber-optic cable does not suffer the same signal losses as coaxial cable, which eliminated the need for so many amplifiers. Decreasing the number of amplifiers made dramatic improvements in signal quality and system reliability and made possible two-way communication over the HFN.
With the introduction of digital signal processing in the late eighties, the analog redistribution system of the fifties entered the digital age. Digital processing and fiber-optic cable made it possible for signals to be sent from the subscriber to the head-end (that is, the “reverse” direction). In the 1990s, cable providers took advantage of the digital architecture to provide Internet access through cable modems. Other services are being planned, including voice over Internet Protocol.
The set top box was originally introduced to convert analog signals from cable head-ends to television channel frequencies that could be viewed on a television. Like other components in the CATV system, the set top box has evolved into an addressable terminal that can be accessed by the CATV system operator and, more recently, that provides a return path for communications initiated by a subscriber. Because current RF matrix switches provide one-way forward path connectivity between head-ends and STBs, there is no automated system for testing the forward path functions of an STB.
It is desirable to implement systems and methods to provide a path for a return signal from an STB to a head-end in a CATV testing environment.